Tandem Pump No-Load Operation Device

ABSTRACT

When the pressure in the main oil supply channel is lower than the no-load operation start pressure, the pressurized oil within the secondary oil supply channel passes through the internal flow channel of the spool and flows into the main oil supply channel. At this time oil output from both the main and secondary oil pumps is merged and supplied to the oil supply destination. When the pressure within the main oil supply channel rises and reaches the no-load operation start pressure, the spool moves in opposite direction to the direction of the force of the spring, the pressurized oil within the secondary oil supply channel is drained, the poppet contacts the spool and blocks the internal flow channel of the spool. At this time, the secondary oil pump enters the no-load operation state, and oil output from the main oil pump only is transmitted to the oil supply destination.

TECHNICAL FIELD

The present invention relates to a tandem pump which comprises two fluid pumps that are driven simultaneously by a single drive source, and in which the pressurized oil output from both fluid pumps is merged and supplied to the fluid supply destination. In more detail, the present invention relates to a tandem pump no-load operation device in which when the fluid supply flow rate increases and the pressure within the fluid supply channel reaches the no-load operation start pressure, one of the fluid pumps is operated under no-load to reduce the power from the drive source.

BACKGROUND ART

A tandem pump includes two fluid pumps that are driven simultaneously by a single drive source, and the pressurized oil output from the respective outlets of the two fluid pumps can be at the same or different pressures. Two separate actuators can be connected to the two outlets of this type of tandem pump and the actuators can be separately operated, but by merging the pressurized oil output from the two pumps and supplying a fluid supply destination, it is possible to obtain a flow rate corresponding to two fluid pumps. An example of the use of the latter tandem pump is an oil pump provided in an automobile engine, for example, that supplies oil (engine oil) to an oil gallery provided in the engine block to lubricate and cool each part of the engine. This is configured so that the drive shaft of the tandem pump is driven by a gear installed on the engine crankshaft. When the engine rotation speed is low, and the flow rate of the oil output from both pumps is small, the oil output from both oil pumps is merged in the oil supply channel, and when the engine rotation speed is large and the flow rate of the oil output from both oil pumps is large, the oil output from one of the two oil pumps is drained and the oil pump is operated under no load, and the oil output from the other oil pump only is supplied to the oil supply channel. In this type of configuration, when the rotation speed of the engine is low, sufficient supply flow rate of lubricating oil can be ensured, so when the vehicle is traveling at low speed it is possible to provide sufficient lubrication to each part of the engine. This type of tandem pump is disclosed in for example Japanese Patent Application Laid-open No. H10-131751 and Japanese Patent Application Laid-open No. 2001-132624.

FIG. 7 shows an example of a conventional tandem pump no-load operation device. In FIG. 7, a main oil pump P1 and a secondary oil pump P2 are driven simultaneously by a single drive source (an engine M). A main oil supply channel L1 is connected to an oil supply destination (for example, an oil gallery provided within the engine block) OB from the outlet of the main oil pump P1 via a line filter that is not shown in the drawings. Also, a secondary oil supply channel L2 that extends from the outlet of the secondary oil pump P2 is connected to the middle portion of the main oil supply channel L1. A check valve CV is installed in the secondary oil supply channel L2 to prevent the inflow of hydraulic oil from the main oil supply channel L1 towards the secondary oil pump P2 side, and an unload valve AV is installed on the secondary oil supply channel L2 between the check valve CV and the secondary oil pump P2.

Here, when the rotation speed of the engine is low, and the pressure within the main oil supply channel L1 is low, the unload valve AV is closed, and the oil output from the secondary oil pump P2 passes through the check valve CV and flows into the main oil supply channel L1, so the oil output from both main and secondary oil pumps P1, P2 is merged and transmitted to the oil supply destination OB from the main oil supply channel L1. On the other hand, when the rotation speed of the engine is high, the flow rate of oil output from both oil pumps increases, and when the pressure within the main oil supply channel L1 is equal to or greater than the no-load operation start pressure, the pressurized oil within the main oil supply channel L1 presses a spool in the unload valve AV which opens the unload valve AV, so the hydraulic oil within the secondary oil supply channel L2 is released to the drain side, and the secondary oil pump P2 enters the no-load operation state. At this time, the pressure in the secondary oil supply channel L2 reduces, and the check valve CV closes the secondary oil supply path L2, so only oil output from the main oil pump P1 is supplied to the oil supply destination OB. Also, a relief valve (pressure regulator valve) LV is provided on the main oil supply channel L1, so that the pressure in the main oil supply channel L1 does not rise above the relief setting pressure.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In the conventional tandem valve as described above there was the problem that the check valve CV and the unload valve AV are provided on the secondary oil supply channel L2 and the relief valve (pressure regulator valve) LV is provided on the main oil supply channel L1 as separate valves, so the freedom of layout is limited in circuit design, and it is difficult to make the entire device compact.

With the foregoing problems in view, it is an object of the present invention to provide a tandem pump no-load operation device having the same performance as a conventional device, but which can be made more compact.

Means to Solve the Problems

The tandem pump no-load operation device according to the present invention comprises: a tandem pump comprising a main fluid pump (for example, the main oil pump 7 in the embodiments) and a secondary fluid pump (for example, the secondary oil pump 8 in the embodiments) that are driven simultaneously by a drive source; a main fluid supply channel (for example, the main oil supply channel 9 in the embodiments) that extends from an outlet of the main fluid pump to a fluid supply destination (for example, the oil supply destination OB in the embodiments); a secondary fluid supply channel (for example, the secondary oil supply channel 10 in the embodiments) that extends from an outlet of the secondary fluid pump and is connected to the middle of the main fluid supply channel; a valve bore that forms a part of the secondary fluid supply channel; a spool disposed by fitting and insertion within the valve bore so that the spool can freely move, having an internal flow channel that extends in an axial direction; an urging member (for example, the spring 30 in the embodiments) that urges the spool within the valve bore toward connection with the main fluid supply channel; and a poppet disposed within the valve bore so as to be able to move freely, that is closer to the connection with the main fluid supply channel than the spool within the valve bore, and that can move to a position in which an end portion of the poppet contacts and closes an end of the internal flow channel of the spool, and to a position in which the poppet is separated from the end of the internal flow channel to open the internal flow channel. Furthermore, a drain channel is provided that is connected to the valve bore, and when the spool is acted on by the pressure within the main fluid supply channel the spool can move against the force of the urging member; when the pressure within the main fluid supply channel is lower than a no-load operation start pressure, the spool is moved by the force of the urging member towards the connection with the main fluid supply channel, the link with the drain channel is closed, and the secondary fluid supply channel and the main fluid supply channel are linked by the internal flow channel; and furthermore when the pressure within the main fluid supply channel rises higher than the no-load operation start pressure, the spool moves against the force of the urging member, and the secondary fluid supply channel is connected to the drain flow channel, and the poppet is moved into a position to contact and close the end of the internal flow channel of the spool by the difference in pressure between the secondary fluid supply channel and the main fluid supply channel resulting from pressurized oil within the secondary fluid supply channel being drained.

Also, in the above tandem pump no-load operation device, it is desirable that a flow channel serving also as a drain opens to both the main fluid supply channel and the external peripheral surface of the poppet is provided within the poppet, and when the pressure within the main fluid supply channel exceeds the no-load operation start pressure and reaches a relief setting pressure that is still higher, the spool is acted on by the force of the relief setting pressure and is moved to a position where the flow channel serving also as a drain and the drain flow channel are connected, and the pressurized fluid within the main fluid supply channel is drained from the drain flow channel.

Advantageous Effects of the Invention

In the tandem pump no-load operation device according to the present invention, when the pressure within the main fluid supply channel is lower than the no-load operation start pressure, the pressurized fluid within the secondary fluid supply channel passes through the internal flow channel of the spool and flows into the main fluid supply channel. At this time the fluid output from the main and secondary fluid pumps is merged and transmitted to the fluid supply destination. When the pressure within the main fluid supply channel rises and reaches the no-load operation start pressure, the spool moves in the direction opposite to the direction of the force of the urging member, the pressurized fluid within the secondary fluid supply channel is drained, the poppet contacts the spool, and the internal flow channel of the spool is closed. At this time, the secondary fluid pump enters the no-load operation state, and oil output from the main fluid pump only is transmitted to the fluid supply destination. In this way, the tandem pump no-load operation device according to the present invention has a configuration in which the necessary components, which are the spool, the urging member, and the poppet, are provided within a single valve bore, while maintaining the same function as the conventional art, namely when the pressure in the secondary fluid supply channel rises and reaches the no-load operation start pressure, the secondary fluid pump enters the no-load operation state which reduces the power from the drive source (and furthermore when the pressure within the main fluid supply channel reaches the relief setting pressure, the pressurized oil within the main fluid supply channel is relieved), therefore the degree of freedom during circuit design is increased, and it is possible to make the overall device more compact.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view showing the configuration of the tandem pump no-load operation device according to an embodiment of the present invention;

FIG. 2 is a partially exploded section view of the no-load operation device;

FIG. 3 is an exploded isometric view of the components within the valve body;

FIG. 4 is a view showing an example of the operation position of the spool and poppet when the oil discharged from both the main and secondary oil pumps merge and is transmitted to the supply destination;

FIG. 5 is a view showing an example of the operation position of the spool and poppet when the secondary oil pump is in the no-load operation state and oil discharged from the main oil pump only is transmitted to the supply destination;

FIG. 6 is a view showing an example of the operation position of the spool and poppet when the outlet pressure in the outlet channel reaches the relief setting pressure and a part of the discharged oil of the main oil pump is drained; and

FIG. 7 is a hydraulic circuit diagram showing an example of the configuration of a conventional tandem pump no-load operation device.

BEST MODE FOR CARRYING OUT THE INVENTION

The following is an explanation of the preferred embodiments of the present invention with reference to the drawings. FIG. 1 shows a tandem pump no-load operation device according to an embodiment of the present invention. The no-load operation device is provided in an automobile engine to transmit under pressure oil (engine oil) that lubricates and cools all parts of the engine to an oil supply destination (for example, an oil gallery provided within the engine block, that is not shown in the drawings) OB, and is assembled into a pump body 1 formed in a part of the crank case of the engine. A pump chamber 2 is formed in the pump body 1, within which a tandem pump 3 is disposed. The tandem pump 3 includes a drive gear 4, and two driven gears (a first driven gear 5 and a second driven gear 6) on either side of and meshing with the drive gear 4, the drive gear 4, the first driven gear 5, and the second driven gear 6 are rotatably supported by a drive shaft 4 a, and driven shafts 5 a, 6 a respectively. The drive shaft 4 a of the drive gear 4 is driven by the crankshaft of an engine (not shown in the drawings) to rotate in the direction of the arrow shown in FIG. 1 (counterclockwise). The first driven gear 5 and the second driven gear 6 rotate in the direction of the arrows shown in FIG. 1 (clockwise) in accordance with the rotation of the drive gear 4.

The drive gear 4 and the first driven gear 5, and the drive gear 4 and the second driven gear 6 constitute conventional gear pumps. In other words, when the drive gear 4 rotates, the first driven gear 5 (or the second driven gear 6) is driven, and hydraulic oil flows in from low pressure portion, and hydraulic oil is expelled from the high pressure portion created by the rotation. In the present embodiment, the part above the portion where the drive gear 4 meshes with the first driven gear 5 is an inlet 7 a, and the part below the meshing portion is an outlet 7 b. Also, the part below the portion where the drive gear 4 meshes with the second driven gear 6 is an inlet 8 a, and the part above the meshing portion is an outlet 8 b. Here, the oil pump that includes the drive gear 4 and the first driven gear 5 is referred to as the main oil pump 7, and the oil pump that includes the drive gear 4 and the second driven gear 6 is referred to as the secondary oil pump 8, the inlet 7 a is referred to as the main oil pump 7 inlet, the outlet 7 b is referred to as the main oil pump 7 outlet, the inlet 8 a is referred to as the secondary oil pump 8 inlet, the outlet 8 b is referred to as the secondary oil pump 8 outlet.

As described above, the tandem pump 3 includes the main oil pump 7 and the secondary oil pump 8 that are driven simultaneously by a single drive source (the engine). Also, a main oil supply channel 9 extends from the outlet 7 b of the main oil pump 7 to which the main oil supply channel 9 is connected, and a secondary oil supply channel 10 (10 a, 10 b, 10 c) extends from the outlet 8 b of the secondary oil pump 8 to which the secondary oil supply channel 10 is connected. The main oil supply channel 9 is connected to an oil supply destination OB which is not shown in the drawings, and as shown in FIG. 1, the secondary oil supply channel 10 (10 a, 10 b, 10 c) is connected to the middle of the main oil supply channel 9. Also, a first oil inlet channel 11 that is connected to the inlet 7 a of the main oil pump 7 is connected to an oil pan T, and a second oil inlet channel 12 that is connected to the inlet 8 a of the secondary oil pump 8 is connected to the middle of the first oil inlet channel 11.

A valve bore 13 is extended in the secondary oil supply channel 10 forming a part of the secondary oil supply channel 10, and a spool 20 whose overall shape is cylindrical is inserted into the valve bore 13 (see also FIGS. 2 and 3). As shown in FIG. 1, the spool 20 includes an intermediate portion 22 having an internal flow channel 21 that extends in the axial direction, and a spring housing portion 23 provided to the left side of the intermediate portion 22 (the left side in FIG. 1), that has a cylindrical shape with a bottom and that is open to the left side, and that is disposed within the valve bore 13 so that the spool 20 can move freely in the direction of extension of the secondary oil supply channel 10. The right end of a spring 30 disposed within a spring housing space 14 formed in the pump body 1 is housed within the spring housing portion 23, and the spool 20 is always forced by the spring 30 to the right (towards the main oil supply channel 9 side). A hollow cylindrical shaped spool stopper 51 and a disk shaped force adjustment fitting 52 are housed within the spring housing space 14, and the spring housing space 14 is closed by an end plate 53 installed in a plate installation groove 15 provided within the pump body 1. The force of the spring 30 can be adjusted as appropriate by changing and using force adjustment fittings 52 of different thicknesses.

At the right end of the valve bore 13 a spool contact surface 13 a is formed in a step shape, and to the right of the spool contact surface 13 a a poppet housing bore 13 d is formed. As discussed later, the poppet housing bore 13 d and an aperture 13 e on the right end thereof form part of the secondary oil supply channel 10.

The spool 20 is acted on by the force of the spring 30 and moves to the right within the valve bore 13, and can move until an end 28 (see FIG. 2) of the spool 20 on the main oil supply channel 9 side (in FIG. 1 the right side of the plane of the paper) contacts the spool contact surface 13 a (see FIG. 2) formed in the valve bore 13, the position of the spool 20 at this time is referred to below as the “initial position”. Also, the spool 20 is positioned in the leftmost position within the valve bore 13 when an end portion 23 a of the spring housing portion 23 contacts an end portion 51 a of the spool stopper 51 (see FIG. 1 and FIG. 2) from the right side, and this is referred to as the “leftmost position”.

A poppet 40 having a cylindrical shape with a bottom, that is open to the side of the main oil supply channel 9, is disposed within the poppet housing bore 13 d, the poppet 40 can move freely along the direction of the axis of the spool 20 within the poppet housing bore 13 d. The poppet 40 has a large diameter trunk portion 41 and a seat portion 42 whose outer diameter is smaller than the outer diameter of the trunk portion 41 and that is located to the left side (the spool 20 side) of the trunk portion 41, and a plurality of linking holes 43 b are formed in the seat portion 42 in the diametral direction.

The seat portion 42 can enter a right side open portion 21 a of the spool 20 from the right (from the side of the main oil supply channel 9). When the seat portion 42 of the poppet 40 is inside the right side open portion 21 a but separated from a valve seat portion 24 formed within the internal flow channel 21 of the spool 20, the internal flow channel 21 of the spool 20 is linked to an internal space 43 a of the poppet 40 via the linking holes 43 b, and furthermore links with the main oil supply channel 9 through the secondary oil supply channel 10 c (in this state, the poppet 40 is said to be in the open position). On the other hand, when the seat portion 42 contacts the valve seat 24, the internal flow channel 21 of the spool 20 is closed at this part by the poppet 40 (in this state the poppet 40 is said to be in the closed position). The channel formed by the internal space 43 a of the poppet 40 and the plurality of linking holes 43 b provided in the outer peripheral surface of the seat portion 42 of the poppet 40 is referred to as a drain multi-use linking channel 43. Therefore, when the seat portion 42 of the poppet 40 is separated from the valve seat 24 of the spool 20, as shown in FIG. 1, the internal flow channel 21 of the spool 20 is linked to the main oil supply channel 9 via the drain multi-use linking channel 43 of the poppet 40 and the secondary oil supply channel 10 c.

A spool rod 25 whose outer diameter is smaller than the outer diameter on both sides is provided in the central portion of the intermediate portion 22 of the spool 20. To the left and right of the spool rod 25 a left and right spool land 26 a, 26 b is formed, and the left and right spool lands 26 a, 26 b are inserted into and mate with the valve bore 13 (13 b, 13 c). A plurality of linking holes 27 is provided along the outer peripheral surface of the left spool land 26 a, and the linking holes 27 connect to the internal flow channel 21. Also, a plurality of drain apertures 29 that penetrates in the diametral direction is formed in the right spool land 26 b to the right of the spool rod 25, and the drain apertures 29 are also connected to the internal flow channel 21.

The secondary oil supply channel 10 is explained as being divided into the part within the valve bore 13 (the channel lob), the part from the outlet 8 b of the secondary oil pump 8 to the valve bore 13 (the flow channel 10 a), and the part from the valve bore 13 to the main oil supply channel 9 (the flow channel 10 c), but the linking holes 27 are positioned so that they are always connected to the flow channel 10 a even if the spool 20 moves from the “initial position” to the “leftmost position”.

A hydraulic oil channel 16 is formed between the outer peripheral surface of the spool rod 25 and a seat bore 13 b of the valve bore 13 and the hydraulic oil channel 16 is connected to a drain channel 17 that that leads to the oil pan T via the second oil inlet channel 12. When the spool 20 is in the initial position, or has moved a small amount to the left from the initial position, the passage between the flow channel 10 a and the hydraulic oil channel 16 is obstructed by the spool land 26 a mating with the seat bore 13 b, but when the spool 20 moves further to the left, the flow channel 10 a and the hydraulic oil channel 16 are linked.

As shown in FIG. 2, to assemble the no-load operation device, the poppet 40, the spool 20, the spring 30, the spool stopper 51, and the force adjustment fitting 52 are inserted into the valve bore 13 (including the poppet bore 13 d) of the pump body 1, then the force adjustment fitting 52 is pressed with a finger to compress the spring 30, and then the end plate 53 is inserted into the plate installation groove 15 of the pump body 1.

In the tandem pump 3 no-load operation device configured in this way, when the drive gear 4 is driven to rotate, the first driven gear 5 and the second driven gear 6 that are meshed with the drive gear 4 also rotate, and the main oil pump 7 and the secondary oil pump 8 operate as pumps. Specifically, the main oil pump 7 draws in oil in the oil pan T through the inlet 7 a, and expels the oil from the outlet 7 b. Also, the secondary oil pump 8 draws in oil in the oil pan T through the inlet 8 a, and expels the oil from the outlet 8 b.

The oil supply destination OB for the expelled oil is the oil gallery within the engine block, and as the flow rate of the supplied oil increases the supply pressure increases. Therefore, when the rotation speed of the engine is low, the flow rate of the oil output by both the main and secondary oil pumps 7, 8 is also small, so the pressure within the oil supply channels 9, 10 is also low. Here, the output pressure from the secondary oil pump 8 acts on the internal flow channel 21, and acts to force the spool 20 to the left. Therefore, the spool 20 moves to the left from the initial position resisted by the force of the spring 30, but the output pressure is low so the amount of movement is small, and as shown in FIG. 4 the passage between the secondary oil supply channel 10 a and the hydraulic oil channel 16 is obstructed by the spool land 26 mating with the seat bore 13 b. During this time, the total amount of oil output into the flow channel 10 a flows into the internal flow channel 21 of the spool 20.

In this way, the oil output from the secondary oil pump 8 that has flowed into the internal flow channel 21 pushes the poppet 40 towards the main oil supply channel 9 side (the seat portion 42 of the poppet 40 is separated from the valve seat 24 of the spool 20) and flows into the main oil supply channel 9 (see the flow of oil indicated by the arrows in FIG. 4). Therefore, the oil output from the main oil pump 7 and the oil output from the secondary oil pump 8 is merged, and transmitted to the oil supply destination OB by the main oil supply channel 9. At this time, the flow rate of oil output from both the main and secondary oil pumps 7, 8 is small, but the two flows are combined and transmitted to the oil supply destination OB, so overall a sufficient supply flow rate of lubricating oil can be ensured.

Next, when the engine rotation speed increases, the flow rate of oil output from both the main and secondary oil pumps 7, 8 also increases, so the pressure within the oil supply channels 9, 10 also increases. As a result the spool 20 moves further to the left. Then when the pressure within the oil supply channels 9, 10 reaches the no-load operation start pressure, and as shown in FIG. 5 when the right end of the spool land 26 a becomes positioned within the flow channel 10 a, the flow channel 10 a and the hydraulic oil channel 16 are linked, so a part of the oil output from the secondary oil pump 8 is returned from the flow channel 10 a to the oil pan T via the hydraulic oil channel 16 and the drain channel 17. In other words, the spool 20 moves to the left resisted by the force of the spring 30, and by connecting the secondary oil supply channel 10 to the drain channel 17, the pressurized oil within the secondary oil supply channel 10 a is drained.

Hence, the pressure within the secondary oil supply channel 10 a and the internal flow channel 21 of the spool 20 drops. As a result, a pressure difference between the pressure within the main oil supply channel 9 and the secondary oil supply channel 10 a is generated, so the poppet 40 moves to the left and is pressed against the valve seat 24 of the spool 20. In this way the link between the main oil supply channel 9 and the secondary oil supply channel 10 a is blocked by the poppet 40, moreover the poppet 40 is pushed by the pressure within the main oil supply channel 9 and forces the spool 20 to the left, so the spool 20 moves further to the left, so the flow rate of pressurized oil returned from the flow channel 10 a to the oil pan T via the hydraulic oil channel 16 and the drain channel 17 increases, and all the oil output from the secondary oil pump 8 is returned to the oil pan T.

In this way, the secondary oil pump 8 enters the no-load operation state, and the power from the drive source (the engine) to drive the tandem pump 3 is reduced. At this time, only the oil output from the main oil pump 7 is transmitted to the oil supply destination OB through the main oil supply channel 9, but the flow rate of the oil output from the main oil pump 7 has already reached a sufficient magnitude, so it is possible to ensure the necessary supply flow rate of lubricating oil to the oil supply destination OB.

Thereafter if the rotation speed of the engine further increases the output pressure within the main oil supply channel 9 corresponding to the increase in the flow rate of the oil output from the main oil pump 7 also increases, and this output pressure acts on the poppet 40. Therefore, the pressure within the main oil supply channel 9 (and the flow channel 10 c) acts on the poppet 40 which moves while pushing the spool 20 to the left. Then when the output pressure from the main oil pump 7 reaches the relief setting pressure, the drain apertures 29 provided on the right spool land 26 b of the spool 20 open into the drain channel 17, and a part of the pressurized oil within the main oil supply channel 9 flows into the drain multi-use flow channel 43 of the poppet 40 from the flow channel 10 c and into the drain flow channel 17 through the drain apertures 29 provided on the spool 20, and is returned to the oil pan T (see FIG. 6). In other words, if the pressure within the main oil supply channel 9 is equal to or greater than the relief setting pressure, the drain multi-use flow channel 43 is connected to the drain flow channel 17 via the drain apertures 29, and the pressurized oil within the main oil supply channel 9 is drained.

This type of drain operation (relief operation) of the pressurized oil within the main oil supply channel 9 by the spool 20 and the poppet 40 is an operation as a relief valve (pressure regulator valve), and the pressure within the main oil supply channel 9 is prevented from exceeding a predetermined maximum pressure (relief setting pressure) by this type of relief operation, so safety of the circuit is ensured.

When the rotation speed of the engine is reduced from the state in which the pressurized oil within the main oil supply channel 9 is relieved as described above, the force with which the poppet 40 pushes the spool 20 to the left weakens, and the spool 20 moves to the right due to the force of the spring 30. Then, when the drain apertures 29 formed in the spool 20 are closed by the seat bore 13 c of the valve bore 13, the flow of pressurized oil from the main oil supply channel 9 to the drain flow channel 17 is stopped, and the above relief operation is terminated (see FIG. 5). Also, when the rotation speed of the engine further reduces, the spool 20 is moved further to the right by the force of the spring 30. Also, when the spool land 26 a of the spool 20 comes into opposition with the seat bore 13 b of the pump body 1, the flow of pressurized oil from the within the secondary oil supply channel 10 (within the flow channel 10 a) to the drain flow channel 17 stops, and the no-load operation state of the secondary oil pump 8 terminates (see FIG. 4).

The “no-load operation start pressure” at which the no-load operation of the secondary oil pump 8 starts and the “relief setting pressure” at which pressurized oil within the main oil supply channel 9 is relieved as described above can be arbitrarily set by the spring characteristics of the spring 30 and the initial displacement (the displacement of the spring 30 when the spool 20 is in the initial position). Therefore, to change the no-load operation start pressure or the relief setting pressure the spring 30 may be changed for a spring with different spring characteristics, or the force adjustment fitting 52 may be changed for a fitting with a different thickness.

In the tandem pump no-load operation device disclosed in the present embodiment, when the pressure in the secondary oil supply channel 10 reaches the no-load operation start pressure, the secondary oil pump 8 enters the no-load operation state and the drive power from the drive source is reduces, furthermore, when the pressure in the main oil supply channel 9 reaches the relief setting pressure, the pressurized oil within the main oil supply channel 9 is relieved, so the same function as the conventional art is maintained, and the necessary components which are the spool 20, the spring 30, and the poppet 40 are provided within a single valve bore 13, so the degree of freedom of layout during circuit design is high, and it is possible to make the overall device more compact.

In the above embodiment, the drain multi-use flow channel 43 that is open to both the main oil supply channel 9 and the outer peripheral surface of the poppet 40 is provided within the poppet 40, and the drain apertures 29 are provided in the valve spool 20, and when the pressure within the main oil supply channel 9 reaches the relief setting pressure, the drain multi-use flow channel 43 is connected to the drain apertures 29, and the pressurized oil within the main oil supply channel 9 is drained, and the spool 20, the poppet 40, and the spring 30 have been configured to function as a relief valve, but the drain multi-use flow channel 43 and the drain apertures 29 may be omitted, and a separate relief valve provided in the main oil supply channel 9. In this configuration, although a separate relief valve is required, the components that perform the function of the check valve and the unload valve in the conventional configuration, namely the spool, the poppet, and the spring, are housed within a single valve bore, so the effect that the configuration can be simplified compared with conventional art can be sufficiently obtained.

So far the preferred embodiments of the present invention have been explained, but the scope of the present invention is not limited to the embodiments described above. For example, in the embodiments described above, an example in which the present invention is provided in an automobile engine to transmit oil under pressure to an oil supply destination OB such as an oil gallery or the like to lubricate and cool each part of the engine was disclosed, but this is an example, and there is no particular limitation on the oil supply destination. Therefore, the oil supply destination of the present invention may be a fluid actuator, and the device may be used to control the operation speed of the actuator in accordance with the load. Also, in the embodiments described above, the fluid output from and supplied by the tandem pump was oil, but the fluid is not limited to oil, and water or air may be used. Also, the two fluid pumps comprising the tandem pump were gear pumps, but provided two fluid pumps are driven simultaneously by a single drive source, other forms of pump may be used (for example, vane pumps, piston pumps, and so on). 

1. A tandem pump no-load operation device, comprising: a tandem pump comprising a main fluid pump and a secondary fluid pump that are simultaneously driven by a drive source; a main fluid supply channel that extends from an outlet of the main fluid pump to a fluid supply destination; a secondary fluid supply channel that extends from an outlet of the secondary fluid pump and is connected to the middle of the main fluid supply channel; a valve bore that forms a part of the secondary fluid supply channel; a spool, disposed by fitting and insertion within the valve bore so that the spool can freely move, having an internal flow channel that extends in an axial direction; an urging member that urges the spool within the valve bore toward connection with the main fluid supply channel; and a poppet disposed within the valve bore so as to be able to freely move, that is closer to the connection with the main fluid supply channel than the spool within the valve bore, and that can move to a closed position in which an end portion of the poppet contacts and closes an end of the internal flow channel of the spool, and move to an open position in which the poppet is separated from the end of the internal flow channel, wherein a drain flow channel is provided that is connected to the valve bore, and when the spool is acted on by the pressure within the main fluid supply channel the spool can move against the force of the urging member; when the pressure within the main fluid supply channel is smaller than a no-load operation start pressure, the spool is moved by the force of the urging member towards the connection with the main fluid supply channel, the link with the drain channel is closed, and the secondary fluid supply channel and the main fluid supply channel are linked by the internal flow channel; and when the pressure within the main fluid supply channel rises higher than the no-load operation start pressure, the spool moves against the force of the urging member, and the secondary fluid supply channel is connected to the drain flow channel, and the poppet is moved into the closed position against the spool by a difference in pressure between the secondary fluid supply channel and the main fluid supply channel resulting from pressurized oil within the secondary fluid supply channel being drained.
 2. The tandem pump no-load operation device according to claim 1, wherein the tandem pump comprises gear pumps comprising a drive gear driven by the drive source and a first driven gear and a second driven gear that circumscribes and meshes with the drive gear.
 3. The tandem pump no-load operation device according to claim 1, wherein the spool comprises: an intermediate portion having the internal flow channel; and an urging member housing portion, at one end of the intermediate portion, that is acted on by the force of the urging member, wherein the external periphery of the intermediate portion is provided, in the center in the axial direction, with a small diameter spool rod portion, and spool land portions are provided to the left and right of the spool rod portion, the left and right spool land portions mate with the valve bore, and the spool is inserted and installed within the valve bore so as to be able to move freely.
 4. The tandem pump no-load operation device according to claim 3, wherein linking holes that penetrate the external peripheral surface and link to the internal flow channel are provided in the left spool land portion, so that within the range of movement of the spool the linking holes are always connected to the outlet side of the secondary fluid pump in the secondary fluid supply channel.
 5. The tandem pump no-load operation device according to claim 3, wherein when the pressure within the main fluid supply channel exceeds the no-load operation start pressure and the spool is moved against the force of the urging member, the secondary fluid supply channel is connected to the drain flow channel via the spool rod portion.
 6. The tandem pump no-load operation device according to claim 1, wherein a flow channel serving also as a drain that opens to both the main fluid supply channel and the external peripheral surface of the poppet is provided within the poppet, and when the pressure within the main fluid supply channel exceeds the no-load operation start pressure and reaches a relief setting pressure that is still higher than the no-load operation start pressure, the spool is acted on by the force of the relief setting pressure and is moved to a position where the flow channel serving also as a drain and the drain flow channel are connected, and the pressurized fluid within the main fluid supply channel is drained from the drain flow channel.
 7. The tandem pump no-load operation device according to claim 6, wherein the spool comprises: an intermediate portion having the internal flow channel; and an urging member housing portion at one end of the intermediate portion of which is acted on by the force of the urging member, wherein the external periphery of the intermediate portion is provided with, in the center in the axial direction, a small diameter spool rod portion, and spool land portions are provided to the left and right of the spool rod portion, the left and right spool land portions mate with the valve bore, and the spool is inserted and installed within the valve bore so as to be able to move freely.
 8. The tandem pump no-load operation device according to claim 7, wherein drain apertures are provided in the right spool land portion that penetrate the external peripheral surface, and that links with a part closer to the main fluid supply channel than a part blocked by the poppet in the internal flow channel, and when the pressure in the main fluid supply channel reaches the relief setting pressure, the spool is acted on by the relief setting pressure and moves to a position where the drain apertures link with the drain flow channel, and the flow channel serving also as a drain is connected to the drain flow channel.
 9. The tandem pump no-load operation device according to claim 4, wherein when the pressure within the main fluid supply channel exceeds the no-load operation start pressure and the spool is moved against the force of the urging member, the secondary fluid supply channel is connected to the drain flow channel via the spool rod portion. 